LGTM

While this fixes the spec to match what browsers have implemented, I'd like to state for the record that I think it is wrong.

IMHO, the behavior should be consistent for both forms. Writing new Date("2015-01-01") should be identical to writing new Date("2015-01-01T00:00:00"), and that form can't be interpreted as UTC because otherwise there'd be no way to specify local time if you wanted to.

Of course, if midnight local time doesn't exist due to DST transition, such as 2016-10-16 in America/Sao_Paulo (Brazil), then 2016-10-16T00:00:00 should adjust forward to the start of the day, which would be 2016-10-16T01:00:00 in this case, which would apply to both date-only and date-time forms.

Hopefully this can be re-addressed in some future version.

@mj1856, in an ideal world, I'd agree with you. But like so many problems with JavaScript, it turned out that this can't be fixed without breaking the web. So I doubt there's ever going to be a chance to rectify it.

FWIW, I also agree :) But I'm going to pull this in now!

Committed as 4f4a37a.